RU145765U1 - DEVICE FOR HYDROACOUSTIC RELIEF SHOT OF THE LOWER SURFACE OF THE ICE COVER - Google Patents

Abstract

A device for hydroacoustic relief shooting of the lower surface of the ice cover, containing linear emitting and receiving antenna arrays perpendicular to each other, signal pre-processing equipment, a device for generating a static fan of receiving directivity characteristics, an echo signal processing device, a multi-channel generator device, a control and display device, and a receiving the antenna array is connected to the input of the signal preprocessing equipment, you One of the signal preprocessing equipment is connected to the input of the device for forming a static fan of receiving directional characteristics, the output of which is connected to the input of the echo signal processing device, the output of the multi-channel generator device is connected to the emitting antenna array, the input of the control and display device is connected to the output of the echo processing device, and the output of the control device and display connected to the input of a multi-channel generator device, to the second input of the equipment pre signal processing, to the second input of the device for forming a static fan of receiving directivity characteristics, to the second input of the device for processing echo signals, characterized in that it further comprises a control device for intrapulse scanning and a device for coordinated filtering of signals with intrapulse scanning, the first input of the device for coordinated filtering of signals with intrapulse scanning is connected to the output of the static fan formation device

Description

The utility model relates to the field of hydroacoustics, namely, hydroacoustic tools designed to capture the topography of the lower surface of the ice sheet by determining distances and directions to the bottom surface of the ice sheet with high angular resolution and distance resolution in a wide observation sector over an immersed object.

Known devices [1, 2] for sonar surveying the topography of the bottom surface, which when changing the direction of radiation of the probe signals relative to the immersed object from the direction "toward the bottom" to the direction "toward the ice surface" [3] solve the same problem of shooting the surface topography and can be considered as analogues.

The principle of operation of analogues is as follows.

There are two mutually perpendicular antennas - emitting and receiving, similar to the Mills cross [4]. The axis of the radiating antenna is oriented parallel to the movement of the immersed object.

For radiation of the probing signals, one directivity characteristic (CI) is formed. Its axis is oriented vertically upward. The radiation CN is “narrow” in cross section in the direction of motion of the immersed object and “wide” in the perpendicular direction.

To receive echoes reflected from the ice surface, I _r ХН (I _r - number of ХН) is formed, forming a static fan in the space above the submerged object. All of them, in contrast to the XI radiation, are "wide" in the cross section of the direction of motion of the object and "narrow" in the perpendicular direction. The axis of the central receiving center is oriented vertically. The axes of the remaining (I _r -1) HN are shifted relative to it by fixed angles α _i , where i is the number of HN (i = 1, 2, ..., I _r in a static fan).

When a probe signal is emitted vertically above the carrier, a band is “illuminated” on the ice surface, narrow in the direction of motion of the immersed object and wide in the perpendicular direction. When receiving from the "illuminated" strip on the surface, narrow sections stand out - elements of angular resolution. The number of angular resolution elements is determined by the number of intersections of receiving CNs with XN radiation, and their angular dimensions are determined by the solid angle, the size of which in the direction of motion of the immersed object is equal to the width of the emitting CN, and in the perpendicular direction, to the width of the receiving CN. This allows you to realize a high angular resolution, both in the longitudinal direction of the immersed object and in the transverse.

Resolution along the coordinate "distance" is determined by the width of the uncertainty function of the selected type of sounding signal, which depends on the frequency band of the sounding signal and the method of its processing.

In each cycle of emission and reception of echo signals within the "illuminated" band are determined:

- the distance to the lower surface of the ice in the resolution element;

- directions to the resolution element of the lower ice surface in the longitudinal and transverse directions of motion of the immersed object.

The coordinates of the resolution elements are determined in the Cartesian coordinate system (SC), attached to the immersed object. In this case, the OX axis is oriented along the direction of motion, the OZ axis is oriented vertically upward, and the direction of the OY axis is chosen to form a right-handed SC.

The “illuminated” band considered above is formed with a stationary submerged object. Its dimensions in the longitudinal direction of motion (X) and in the transverse direction (Y) are equal to:

where Δα is the width of the central emitting CN;

ΔB is the viewing sector angle of the receiving antenna;

H is the depth of the submerged object.

To capture the relief of the ice surface of the required area, the “illuminated” strip is moved due to the movement of the submerged object. At time instants t _j = t ₀ + j · T, where t ₀ is the initial time, T is the radiation period of the probing signals, j is the radiation number, j = 0, 1, ..., J-1, J is the number of emissions. If the speed of movement (V) is constant in magnitude and direction, they correspond to the position of the submerged object X _j = X ₀ + j · V · T, where X ₀ is the initial value of the X coordinate. For the period T, the distance is determined in each i-th receiving XN to the immersed object (R _{j, i} ) by the delay of the echo signal coming from the resolution element. Then, taking into account the inclination angle of the receiving XN (α _i ), the vertical (Z _{j, i} ) and horizontal (Y _{j, i} ) coordinates of the selected surface area — the resolution element in the SC of the immersed object are calculated according to the formulas:

To improve the accuracy of determining the coordinates of resolution elements, in some cases, the geometric curvature of the rays along which the emitted and received signal propagates due to a change in the speed of sound along the propagation path of the probe signal [4] is taken into account.

To eliminate omissions in the "lighting" of the surface, the speed of the immersed object is limited by the condition:

It follows from condition (3) that the higher the angular resolution of the radiating antenna (the smaller the width of the radiating HN), the lower the speed should be and, accordingly, the longer it takes to record the relief of the ice surface of the required area.

The closest to the claimed device prototype is a multi-beam echo sounder SeaBat 7125 [1].

The prototype consists of:

- a radiating antenna array (AR);

- a multichannel generator device (MSU) that generates emitted signals in each sonar transducer (HAP) emitting AR;

- receiving antenna array;

- signal pre-processing equipment (APOS), which provides band-pass filtering, amplification and analog-to-digital conversion of the signal received by each HAP receiving AR;

- devices for the formation of a static fan receiving HN;

- devices for processing echo signals;

- control and display devices.

The disadvantages of the prototype:

- Low shooting performance of the relief of the lower surface of the ice above the submerged object (by the shooting performance is understood the shooting area performed in one review cycle), which is due to the limitation of the speed of movement of the immersed object according to relation (3) and, accordingly, the long shooting time for a given area. This also leads to a limitation of the shooting area at a given time.

- A narrow area for surveying the relief of the lower surface of ice above an immersed object at zero speed of an immersed object due to the narrow width of the directivity of the emitting antenna array, which leads to a large time for determining the size of wormwood and spreads during special maneuvering of an immersed object before ascent.

The objective of the utility model is:

- improving the shooting performance of the relief of the lower surface of the ice over an immersed object;

- providing a survey of the relief of the lower surface of the ice above an immersed object at zero speed of the immersed object.

The technical result of the claimed device is to obtain a three-dimensional relief of the lower surface of the ice of a large area for a minimum time at any, including zero, speeds of the submerged object.

The technical result of the claimed device is achieved through the use of intrapulse scanning when emitting sounding parcels, which allows you to form several emitting CNs in one radiation-reception cycle, illuminating a large area of the lower surface of ice above an immersed object.

Intra-pulse scanning is as follows. The emitted signal in each radiation-reception cycle consists of a set of "elementary" orthogonal signals. Each elementary orthogonal signal is sequentially radiated in its own specified direction. In this case, sequential "lighting" (scanning) of the lower surface of the ice occurs. Direction of radiation is provided by introducing the necessary delays into the elementary signals in a similar way to what happens when forming a static fan of an XN receiving AR. When receiving due to the orthogonality of elementary signals, they are divided along the directions of radiation of the elementary signal. This allows you to "illuminate" a large sector of the lower surface of the ice with increased spatial resolution in one cycle of radiation-reception.

Orthogonal elementary signals are formed according to the following rule.

The basic sequence of pulses is formed. The number of pulses in it is M. The duration of each pulse is Ti. The center frequencies of the pulses are determined by the formula:

where: m - serial number of the pulse in the basic sequence, m = 0, 1, ... M-1;

F _min - the lower limit of the frequency band of the emitted signal;

DFi = 1 / Ti - frequency band of a single pulse;

Orthogonal elementary signals are formed from the basic pulse sequence in one of the following ways:

a) elementary signals represent single pulses at a given frequency, determined by the formula (4), with each pulse being emitted in the direction given to it;

b) elementary signals are formed from orthogonal sequences of M pulses, for example, the Costas sequence [5], and each sequence of pulses is radiated in a given direction.

Upon receipt, filtering is consistent with the type of probe signal.

To ensure the claimed result, new elements are introduced, namely:

a) an intrapulse scanning control device;

b) a device for coordinated signal filtering with intrapulse scanning.

The block diagram of the inventive device is shown in FIG. one.

In FIG. 1 adopted the following notation:

1 - radiating antenna array

2 - multi-channel generator device

3 - control device intrapulse scanning,

4 - receiving antenna array

5 - signal preprocessing equipment,

6 - a device for forming a static fan of receiving directivity characteristics,

7 - device consistent filtering signals with intrapulse scanning,

8 is a device for processing echo signals,

9 - control and display device. The device operates as follows.

When you turn on the control and display device 9 for each radiation-reception cycle, the operating mode parameters are assigned:

- in the control device intrapulse scanning 3: the parameters of the intrapulse scanning - the number of directions and their angles, and the parameters of the orthogonal elementary signals - the number in the sequence, frequency and duration of the pulses;

- in multi-channel generator device 2: parameters for each HAP used in the formation of radiation in one direction - power, sequence of delays, frequencies, signal durations;

- in the signal preprocessing equipment 5: the same parameters as in devices 2 and 3, which is necessary to coordinate the operation of the equipment with the emitted signals;

- in the device for forming a static fan of the receiving directivity characteristics 6: parameters ensuring the formation of the XN fan - the number of XN, their directions and the corresponding delays in each HAP channel;

- in a device for coordinated filtering of signals with intrapulse scanning 7: parameters of the emitted signals - the number and type of elementary orthogonal signals, the directions of their radiation;

- in the device for processing echo signals 8: parameters that determine the delay of the echo signal, including the time stamp of the radiation moment, the coordinates of the resolution element of the lower ice surface to form a three-dimensional (X, Y, Z) display of the lower ice surface - the coordinates of the origin of the antenna coordinate system, angles heading, roll and trim, vertical section of the speed of sound.

Having received the assigned operating mode from the control and display device 9, the intrapulse scanning control device 3 generates a predetermined set of elementary orthogonal signals, which are transmitted to the multi-channel generator device 2.

A multi-channel generator device 2 for each HAP in the radiating antenna array 1 introduces the time delays of the elementary orthogonal signal corresponding to the assigned direction of radiation, and transmits this signal with delays to the radiating antenna array 1.

The radiating antenna array 1 emits an elementary signal in a designated direction.

Then, the device 2 introduces time delays for the next elementary orthogonal signal, transfers it again to the radiating antenna array 1, which produces radiation in the next direction. The cycle is repeated until the number of directions selected in this radiation-reception cycle has been exhausted.

The receiving antenna array 4 receives the signals reflected by the ice surface and transmits them to the signal preprocessing equipment 5.

The signal preprocessing equipment 5 performs filtering, amplification, and analog-to-digital conversion of the signals received in each HAP channel of the receiving antenna array 4 and transmits them to the device for forming a static fan of receiving directivity characteristics 6.

The device for forming a static fan of the receiving directivity characteristics 6 introduces into the signals from the output of each channel of the HAP receiving antenna array 4, time delays corresponding to the designated directions of the fan of the receiving directivity characteristics. For each direction, it sums up signals from all HAPs. The total signal is a signal from a given direction of XH reception. Then, the signals from the output of all receiving CNs of a static fan are transmitted to a device for coordinated signal filtering with intrapulse scanning 7.

The coordinated signal filtering device with intrapulse scanning 7 performs multichannel matched filtering of echo signals following from the output of all receiving CNs. The impulse characteristics of the channels of a multichannel filter are equal to the emitted elementary orthogonal signals. As a result of multichannel filtering in each direction, the numbers of emitted elementary signals, which correspond to the directions of the emitting CN, are determined from the static fan of the receiving CNs. Thus, echo signals are formed corresponding to the directions to the resolution element in the longitudinal and transverse planes of motion of the immersed object. They are transmitted to the echo signal processing device 8.

The device for processing the echo signals 8 for each direction to the resolution element determines the delay in the arrival of the echo signal and determines the distance to the resolution element from it. Then it calculates the coordinates of the resolution element in a rectangular coordinate system using the obtained distances and directions defined in the device 7. These coordinates are transmitted to the control and display device 9.

The control and display device 9 performs the construction and display of a three-dimensional relief of the lower surface of the ice.

The principle of operation of the inventive device provides various modes of operation, including:

(A) —operation mode when using one XN radiation in each radiation-reception cycle,

(B) - an operating mode in which an overview of the space above an immersed object is provided in a wide sector of the angles of direction of the XL radiation.

In mode (A), the inventive device operates as a conventional multi-beam echo sounder. In mode (B), intrapulse scanning is used and the claimed technical result is provided.

The practical use of intrapulse scanning is illustrated by the following.

Each moment of time corresponds to a volume of space that reflects or scatters the incident acoustic field, which is a resolution element. The scope of the permission element is:

Where - the distance of the resolution element at time X,

α - radiation direction, relative to the horizontal plane,

- distance resolution element,

ΔF is the band of the probe signal,

c is the average speed of sound in water,

Δα, Δβ are resolution elements that are equal to the width of the radiating (Δα) and receiving (Δβ) CN, respectively.

Let the entire field of view be: R — in distance, ΔA — angle of the field of view in the longitudinal plane of motion of the immersed object, and ΔB — in the transverse plane. To view it, taking into account a parallel survey of the receiving antenna in a sector of size ΔB, using one radiating HN takes time:

The inventive device allows to reduce the viewing time determined by the ratio (6).

In the inventive device, a radiating signal is formed, consisting of K _{s of} elementary orthogonal signals (K _s is the number of signals). The radiating antenna array 1 radiates sequentially each elementary orthogonal signal into a separate XN radiation. In this case, sequential “lighting” (scanning) of the strip of the lower ice surface occurs, the width of which is K _s times wider than that of the prototype. When receiving echo signals due to the orthogonality of the elementary signals in each XN of a static fan, the direction of the incoming echo signal is determined corresponding to the direction of emission of the elementary signal. As a result, the survey time determined by relation (6) is reduced by a factor of K _s . The described principle of viewing the lower surface of the ice is illustrated in FIG. 2. In FIG. Figure 3 shows the field of view of space for one radiation cycle.

The ability to obtain when implementing a utility model of the specified technical result is determined on the basis of theoretical estimates of the effect obtained using the inventive device, compared with the prototype:

The prototype provides the performance of shooting the relief of the lower surface of the ice over an immersed object, taking into account formula (1), equal to:

where Tc is the time of one review cycle.

The inventive device in mode (B) above, provides a shooting performance of the relief of the lower surface of the ice over an immersed object, equal to:

where ΔA is the angle of the viewing sector in the longitudinal plane of motion of the immersed object, which provides intrapulse scanning.

Thus, the increase in the productivity of the review of the relief of the lower surface of the ice above the submerged object of the claimed device, in relation to the productivity of the prototype will be:

In particular, at Δα ₀ ≈1 °, ΔA≈ ± 45 °, the gain in productivity will be K _P ≈60.

At zero speed of the immersed object, the prototype provides an overview of the relief of the lower surface of the ice above the immersed object, the area of which is determined by the formula:

At zero speed of the immersed object of the claimed device provides an overview of the relief of the lower surface of the ice above the immersed object, the area of which is determined by the formula:

Thus, the increase in the viewing area of the relief of the lower surface of the ice above the submerged object at zero speed of the submerged object, the claimed device, relative to the viewing area of the prototype will be:

and coincides with an increase in shooting performance, which is estimated by the formula (9).

Bibliography.

1. SeaBat 7125; www.mnsspb.ru, the site of CJSC Marine Navigation Systems.

2. "High-resolution sonar - sound recorder" developed by Acoustical Institute named after academician NN Andreev OJSC (www.akin.ru)

3. Jerevy P. Wilkinson, Peter Wadhams and Nick E. Hughes. “A review of the sonar underwater vehicles to obtain information on sea ice draft.” - “Arctic sea ice thickness. Past, present & future ”. International workshop, Rungstedgaard, Denmark, 8-9 november, 2005.

4. Urik Robert J. Fundamentals of hydroacoustics. // Per. from English - L .: Shipbuilding, 1978.

5. Costas, J.P. (1984). “A study of a class of detection waveforms having nearly ideal range - Doppler ambiguity properties.” Proceedings of the IEEE 72 (8): 996-1009.

Claims (1)

A device for hydroacoustic relief shooting of the lower surface of the ice cover, containing linear emitting and receiving antenna arrays perpendicular to each other, signal pre-processing equipment, a device for generating a static fan of receiving directivity characteristics, an echo signal processing device, a multi-channel generator device, a control and display device, and a receiving the antenna array is connected to the input of the signal preprocessing equipment One of the signal preprocessing equipment is connected to the input of the device for forming a static fan of receiving directional characteristics, the output of which is connected to the input of the echo signal processing device, the output of the multi-channel generator device is connected to the emitting antenna array, the input of the control and display device is connected to the output of the echo processing device, and the output of the control device and display connected to the input of a multi-channel generator device, to the second input of the equipment pre variable signal processing, to the second input of the device for forming a static fan of receiving directivity characteristics, to the second input of the device for processing echo signals, characterized in that it further comprises a control device for intrapulse scanning and a device for coordinated filtering of signals with intrapulse scanning, the first input of a device for coordinated filtering of signals with intrapulse scanning is connected to the output of the static fan formation device directivity characteristics, the second input is connected to the second output of the intrapulse scanning control device, the third input is connected to the output of the control and display device, the first output of the intrapulse scanning control device is connected to the second input of the multi-channel generator device, the input of the intrapulse scanning control device is connected to the output of the control device and display.